Đáp án:
Câu 3.
$A = 5\sqrt{8} + \sqrt{50} - 2\sqrt{18} = 5\sqrt{4.2} + \sqrt{25.2} - 2\sqrt{9.2} = 10\sqrt{2} + 5\sqrt{2} - 6\sqrt{2} = 9\sqrt{2}$
Câu 4.
$A = \sqrt{27} - 2\sqrt{12} - \sqrt{75} = \sqrt{9.3} - 2\sqrt{4.3} - \sqrt{25.3} = 3\sqrt{3} - 4\sqrt{3} - 5\sqrt{3} = -6\sqrt{3}$